Portable electric tool



March 29, 193s. F. Rmss PORTABLE ELEOTRIC TOOL original Eiledbuiy 23,1954 l ATTORNEY.

. the commutator segments tothe windings of the i Patented Mar. 29, 1938 UNITED STATE s PAT-ENT y' ori-fici;`

PORTABLE ELECTRIC Toon Frithiof P. Forss, Aurora, In., assignm- Vto ln-v dependent Pneumatic Tool' Co., Chicago, Ill., a vcorporation of Delaware v Original yapplication July 23, 1934, Serial No. Divided and this application March z3, 193e, serial No. 10,241

4 claims.' (c1. 5'1--1roi tween them. These wires, by reason of the close spacing between the commutator and the armature, are relatively short, extending directly from armature. These wires rotate as a group with the-armature and the commutator and in tools as heretofore constructed are injured by the vibrations transmitted to the armature from the driving shaft or spindle of the tool. These vlbrations are especially severe in rotary grinders,

wherein a grinding wheel is directly connected to and rotated by the spindle of the tool. This vibration crystallizes the lead wires, causing them to break o i and short circuit the motor of the tool. This vibration also subjects the gearing and the bearings in thetool to undue wear.

The general purpose and object of myinvention is to provide means in the tool between the grinding wheel and the motor to eliminate or deaden these vibrations and thus prevent crystalliza tion and breaking of the lead wires and also undue Wear on the gearing and the bearings.

In carrying out the object of my invention, I provide the driving shaft or spindle of the tool with a exible section so constructed and arranged that vibrations generated by the grinding wheel when in operation will not injure the lead wires or produce undue wear on the gearing or the bearings of the tool.

The invention consists further in the features hereinafter described and claimed.

Fig. 1 is a longitudinal sectional view with parts in elevation of a portable electrically operated grinder embodying the flexible shaft section of my invention;

Fig. 2 is a larger view of the flexible shaft sec# tion and the portion of the tool containing the same to more clearly illustrate the construction; and

Fig. 3 is a transverse sectional view taken on line 3-3 of Fig. 2.

In the drawing, I indicates the electric motor of the tool having a stator 2 and an armature 3. The armature is disposed within the stator and is keyed or otherwise xedly secured to the armature shaft 4. The latter extends beyond the opposite ends of the armature and is journaled at its ends in anti-friction bearings 5, 6 lsupportedin the outer casing of the tool.A The forward end of the shaft 4 is provided with gear teeth 1 which mesh with a speed reducing gear pinion k8 fixed to the inner end portion 9 of the spindle or driving shaft of the tool, to be presently described. "'Ihe opposite end of the shaft 4 supports a commutator I0 engaged by theusual brushes, one of which is shown at I,If. The brushes are connected withl the current supply ywires for the tool through a switch device I2 in the handle section I3 ofthe tool. The switch device has amanually operable actuating member `I4 accessible from the exterior of the handle section and slidably mounted therein as shown. The supply wires extend into the handle section through a carrying tube I5 as shown. '5

The commutatorl I0 is located closely adjacent the armature 3 and the lsegments of@ the come mutator are connected with the windings of the armature by a plurality of lead wires I6, I6' ar'- ranged in an annular group between 4the commutator and the armature@v By reason of the close spacing of these parts, the lead wires I6 are relatively short and extend directly from the conimutator to the armature.

l The'spindle of the tool, in accordance withiny" n invention, contains a flexible section cor'nprising the inner portion 9 heretofore referred to, afor.- ward portion I1 and an intermediate portionconsisting of a pile of thin liexible'steel blades I8, I9.

The blades extend between and connect the spindle portions 9 and I1 for the rotation of one byk the other. To' accomplish this, the blades extend into transverse slots I9, I9 in the spindle sectionsl as shown. The blades are arranged to have flat- Wise contact with each other and thusmutually support one another to provide a solid driving connection for the spindle sections. vThe blades are enclosed in a sleeve 20 which extends between the spindle sections and fits about the same as shown. Thus, the sleeve prevents displacement of the blades from the slots, the sleeve extending over the slots at the sides of the spindle sections as illustrated in Fig. 3. It will be observed that the blades ll the slots-and have their side edges in contact with the inner surface of the sleeve.

The sleeve 20 has a pressed fit on the spindle p section I1 and a rotative t on the section 9. Thus the section I1 may turn relatively to the section 9 in response to a torque strain irn-v y parted to the section I'I by the grinding wheel 2l secured to its outer end. This torque strain twists or exes the blades I8 in a radial or spiral dumm. u 'maimed by me dotted une;v m

' m. s. and me vibrations ums imparted to the spindle by the grinding wheel are absorbed or' deadened in the spindle'- and are not transmitted to the armature shaft oi' the motor to crystallize and break the lead wires Il, as heretofore. Morelover. .tbe bearings and ythe gearing ofthe tool are.:also'relievedfoi' these strains and' undue wearonthesepartsistoalargeextenteliminated. 'Riese strains are especially severe inthe work. the speed o! the wheel is suddenly re-v duced by the frictional resistance oiIered to its rotation -and the shock so imparted to the spin-- die is takenv up by the blades II-which iiex or twist in response to this. applied strain. These shocks are repeatedly applied to the spindle as the grinding wheel is movedover the work. the rotation of the wheel being retarded as it contacts with the work and accelerating as it is lifted from or frees the work. With the spindle sections.. 'and l1 relatively rotatable, the blades mayy twist or tlex in response lto these torque strsins,-and the tool partsdand the lead wires to therear Vof the'blades will be relieved of these shocks and Jars. Thus, the lead wires in partisular will be protected from breakage and short lcircuitzlng ofl the motor willbe prevented.

The blades Il have a loose vor sliding nt in the slots Il and the latter have their outer ends rbeveled outwardly. at 2l t0 facilitate twisting oi' the blades. The ends of the bladesv abut against theends ofthe slots. The bearings 23,

u journal the spindle in the tool casing which is provided for thespindle and this casing is secured to themotorcase 26 at its end oppodte Ithe, handle section Il. The bearing 24 v dle driven by said motor,'a tool member mounted which journals the spindle section Il in the casthe' casing 2l by the bearing 4'23, and the inner ing!! is .clamped 'solid' in the casing by a ring nut .2L-"111e spindlesection I is journaledin end lot this section is opposite an abutment 2s carried by a fixed part ofk the tool casing, as for example the plate 2l whichis clamped Vbetween the casings ,2l and 2l to divide one from the other and which plate also provides a support for the bearing i for the armature shaft 4. Abutment 2l is provided to limit the endwise movealiases ment of the spindle section i toward motor l. The ring nut 21 is screwed into the opposite end oi the casing 25.' the llatter being internally screw threaded to receive the nut. 'Ihe bearings are ot the anti-friction type ss'shown. I'he blades will twist in response to those'torque strains which enable or cause one spindle secvtion to rotate relatively 'to tbe-otherand thus relieve one section oi shocklor Jar imparted to the v I The detalls o! construction and arrangement 1o"4 rpm-ts shown and describes-may be variousiv.

changed and modied without departing from the spirit and scope of my invention except as pointed out in the appended claims. A.;

I claim as' my invention: vl. In a portable tool.` an electric motor, a spindle vdriven by said motor, a tool member mounted for direct drive on the spindle. and torque responsive means incorporated in the spindle to relievethe motorl of vibrations imd parted to the spindle by the tool member in the use of the tool.

2. In a portable tool, an electric motor, a'spinf dle driven by said motor, a tool member mounted i'or direct drive on the spindle. and vtorque responsive means consisting oi exible blade means incorporated in the-spindle to relieve the motor oi `vibrations imparted to the spindle' by the tool member in the use oi the tool.-

3. In a portable tool, an electric motor, a

spindle driven by said motor, a tool member 7 mounted ior direct drive on- .tbe spindle,A the latter having axially spaced sections. andtorque responsive means consisting oi' Ilexible blade means extending between and ilttlng in slots in said sectionsv to relieve the motor of vibrations imparted to the spindle bythe tool member in the use oi the tool.

4. In a portable tool, an .electricI motor, a spinfor direct drive on the spindle. the latter having axially spaced sections, torque responsive means consisting of flexible blades extending between and iitting in slots in said sections to relieveby the tool member in the use oi' the tool, and a k thev motor of vibrations impartedto' vthe spindle` sleeve element about -theblades and the spindle i r'nrrmony r.' Fonss.

' sections to hold the blades between lthe sections and in the slots.

i i l 

